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.TH PTHREAD_MUTEXATTR_GETTYPE 3C "Mar 23, 2005"
.SH NAME
pthread_mutexattr_gettype, pthread_mutexattr_settype \- get or set mutex type
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
#include <pthread.h>

\fBint\fR \fBpthread_mutexattr_gettype\fR(\fBpthread_mutexattr_t *restrict\fR \fIattr\fR,
     \fBint *restrict\fR \fItype\fR);
.fi

.LP
.nf
\fBint\fR \fBpthread_mutexattr_settype\fR(\fBpthread_mutexattr_t *\fR\fIattr\fR, \fBint\fR \fItype\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBpthread_mutexattr_gettype()\fR and \fBpthread_mutexattr_settype()\fR
functions respectively get and set the mutex \fItype\fR attribute. This
attribute is set in the \fItype\fR parameter to these functions. The default
value of the \fItype\fR attribute is \fBPTHREAD_MUTEX_DEFAULT\fR.
.sp
.LP
The type of mutex is contained in the \fItype\fR attribute of the mutex
attributes. Valid mutex types include:
.sp
.ne 2
.na
\fB\fBPTHREAD_MUTEX_NORMAL\fR\fR
.ad
.RS 28n
This type of mutex does not detect deadlock. A thread attempting to relock this
mutex without first unlocking it will deadlock. Attempting to unlock a mutex
locked by a different thread results in undefined behavior. Attempting to
unlock an unlocked mutex results in undefined behavior.
.RE

.sp
.ne 2
.na
\fB\fBPTHREAD_MUTEX_ERRORCHECK\fR\fR
.ad
.RS 28n
This type of mutex provides error checking. A thread attempting to relock this
mutex without first unlocking it will return with an error. A thread attempting
to unlock a mutex that another thread has locked will return with an error. A
thread attempting to unlock an unlocked mutex will return with an error.
.RE

.sp
.ne 2
.na
\fB\fBPTHREAD_MUTEX_RECURSIVE\fR\fR
.ad
.RS 28n
A thread attempting to relock this mutex without first unlocking it will
succeed in locking the mutex. The relocking deadlock that can occur with
mutexes of type \fBPTHREAD_MUTEX_NORMAL\fR cannot occur with this type of
mutex. Multiple locks of this mutex require the same number of unlocks to
release the mutex before another thread can acquire the mutex. A thread
attempting to unlock a mutex that another thread has locked will return with an
error. A thread attempting to unlock an unlocked mutex will return with an
error. This type of mutex is only supported for mutexes whose process shared
attribute is \fBPTHREAD_PROCESS_PRIVATE\fR.
.RE

.sp
.ne 2
.na
\fB\fBPTHREAD_MUTEX_DEFAULT\fR\fR
.ad
.RS 28n
Attempting to recursively lock a mutex of this type results in undefined
behavior. Attempting to unlock a mutex of this type that was not locked by the
calling thread results in undefined behavior. Attempting to unlock a mutex of
this type that is not locked results in undefined behavior. An implementation
is allowed to map this mutex to one of the other mutex types.
.RE

.SH RETURN VALUES
.sp
.LP
Upon successful completion, the \fBpthread_mutexattr_settype()\fR function
returns \fB0\fR. Otherwise, an error number is returned to indicate the error.
.sp
.LP
Upon successful completion, the \fBpthread_mutexattr_gettype()\fR function
returns \fB0\fR and stores the value of the \fItype\fR attribute of \fIattr\fR
in the object referenced by the \fItype\fR parameter. Otherwise an error number
is returned to indicate the error.
.SH ERRORS
.sp
.LP
The \fBpthread_mutexattr_gettype()\fR and \fBpthread_mutexattr_settype()\fR
functions will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value \fBtype\fR is invalid.
.RE

.sp
.LP
The \fBpthread_mutexattr_gettype()\fR and \fBpthread_mutexattr_settype()\fR
functions may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value specified by \fIattr\fR is invalid.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR pthread_cond_timedwait (3C),
.BR pthread_cond_wait (3C),
.BR attributes (7),
.BR standards (7)
.SH NOTES
.sp
.LP
Application should not use a \fBPTHREAD_MUTEX_RECURSIVE\fR mutex with condition
variables because the implicit unlock performed for \fBpthread_cond_wait()\fR
or \fBpthread_cond_timedwait()\fR will not actually release the mutex (if it
had been locked multiple times). If this occurs, no other thread can satisfy
the condition of the predicate.
